1. Field of the Invention
The present invention relates to a control apparatus of an automatic transmission having a gear mechanism and a method of controlling the same.
2. Related Background Art
A conventional example of an automatic transmission having a gear transmission mechanism is disclosed in Japanese Patent Unexamined Publication No. 61-45163. In this conventional one, the fastest gear of the gear transmission is locked or released by using a friction clutch, and the engine revolutions are controlled by sliding the friction clutch to change the speed at the gear change operation in synchronization with the revolutions of an output shaft, thus enabling a smooth gear change.
This automatic transmission, however, has a problem that, if the friction clutch has only a small torque capacity, a gear change in a high output shaft torque condition causes a driver and the like to feel odd due to a difference from a torque that can be generated by the friction clutch transmitted as a torque change to the output shaft.
It is an object of the present invention to provide a control apparatus of an automatic transmission making possible a smooth gear change with a smooth shift of output shaft torque even if output shaft torque is high at the gear change.
Therefore, to solve the above problem in accordance with an aspect of the present invention, there is provided an automatic transmission, having torque transmission means between an input shaft and an output shaft of a gear transmission, the torque transmission means on at least one gear change stage serving as a friction clutch, and the torque transmission means on other gear change stages serving as claw clutches, for changing speed smoothly by controlling the friction clutch at a gear change from one gear change stage to another, wherein, if output shaft torque exceeds limit transmission output shaft torque obtained by a torque capacity of the friction clutch multiplied by a gear ratio provided for the friction clutch when a gear change command is issued in the automatic transmission, engine torque is controlled so that the output shaft torque becomes equal to the limit transmission output shaft torque and then an engine torque control is switched when the output shaft torque reaches the same value as the limit transmission output shaft torque to start to change the speed.